The Picture Rock quarry is 3.5 kilometres northwest of Midway, directly under a major hydroelectric power line. Access is by a dirt road to the power line from the former railway crossing on Highway 3, west of Midway. The quarry is 500 metres southwest of the Midway mine (082ESE128), from which about 19 tonnes of silver and gold ore with lead and zinc credits were shipped in the late 1960's and early 1970's.
The Rainbow claims covering the area have been explored for large tonnage precious metal potential by Dentonia Resources and Kettle River Resources in 1983, Kerr Addison Mines Ltd. in 1984, BP Resources Canada Ltd. from 1987 to 1989 and Minnova Inc. in 1989 and 1990. Through this period to present, ornamental chalcedony has been obtained from the Picture Rock locality for lapidary purposes.
At the Picture Rock Quarry, epithermal chalcedonic veins cut altered serpentinite (listwanite) and feldspar porphyry dikes. The quarry is actually a group of small detached and interconnected pits developed over a radius of several tens of metres on the crest of a low ridge. The veins are generally narrow (up to 50 centimetres wide) and mostly shallow dipping to the east and northeast. Typically the veins are delicately banded in white, grey, light blue and blue-green layers that are developed parallel to the veins walls or around listwanitic breccia clasts. Except for the largest veins, seen by the floor of the main pit, which has a hangingwall composed mostly of dickite several centimetres thick, walls are a little altered by the veining. The veins have epithermal gold, silver, arsenic, antimony signatures, with anomalous but subeconomic precious metal values.
The Picture Rock chaledonic quartz has proven attractive for the manufacture of clock faces and ornaments by local artisans. The bluish-green colour of some of the chalcedony was thought to be due to the presence of nickel, as chrysoprase, derived from the ultramafic and listwanitic host rocks. However, analysis of a sample of the bluish vein material yielded only 15 parts per million nickel. Other elements, possibly contributing to the colour, include 71 parts per million cobalt, 94 parts per million manganese, 0.46 per cent iron, 538 parts per million strontium, 96 parts per million chromium, 100 parts per million niobium, and 641 parts per million tungsten.
An epithermal quartz breccia system occurs along the surface trace of a thrust fault, at the Picture Rock Quarry. A small amount of chalcedony and chalcedonic breccia has been quarried from this area for ornamental, decorative stone. Previous workers had reported elevated gold values (to 0.58 grams per tonne gold) from surface samples at the Picture Rock Quarry. During 2003, trenching was done to further explore the epithermal quartz breccia system in the vicinity of the quarry. A generally east-west trending, gently north dipping breccia vein was discovered to the east of the quarry, in Trench 03-8. The vein yielded an average of 0.43 gram per tonne gold across a 1.8 metre true width, with values to 1.2 grams per tonne gold and 1 gram per tonne silver (Assessment Report 27466). A drill hole by BP Resources in 1987 (ddh 87-1) tested this area at depth. An increase in alteration was noted at the base of the drill hole and workers at the time suggested deepening this hole, however this was not completed.
Anomalous gold, to 2.6 grams per tonne gold, occurs in similar looking, chalcedonic breccia vein a few hundred metres to the west on Lone Boulder Hill; trenching during 2003 exposed a steeply dipping, north trending, siliceous breccia zone within listwanite in Trench 03-1, which yielded values to 1.14 grams per tonne gold over the 2 metre true width (Assessment Report 27466).
A chalcedony vein is reported in outcrop about 400 metres to the south of the Picture Rock Quarry, which yielded 3.2 grams per tonne gold and 3.1 grams per tonne silver over 0.6 metres (Assessment Report 17162). This zone was drilled by BP as hole 87-2 but yielded only low precious metal values.
In 2003, Gold City Industries Ltd. carried out a trenching and sampling program on their Midway gold property. Work focused on the Picture Rock Quarry area. In 2004, Gold City established three grids on the Midway property near the quarry totaling 15.2 kilometres and 704 soils samples were collected. Merit Mining Corp. (formerly Jantri Resources Inc.) exercised its option to acquire a 100 per cent interest in Gold City Industries Ltd.’s British Columbia assets, pursuant to an option agreement dated September 15, 2004.
In 2004, Gold City Industries Ltd. expanded the soil grids over the Picture Rock and Lone Boulder Hill areas. Multiple zones of anomalous gold with a max grade of 426 parts per billion were observed (Banas, A., Dufresne, M. (2013-11-25): Technical Report for the Greenwood Gold Project).
In 2009, Grizzly Discoveries Inc. conducted an airborne EM and magnetic survey. The results showed a number of conductors and weak electromagnetic anomalies associated with the Midway Window and areas underlain by Eocene volcanic and sedimentary rocks.
In 2011, Infinity Minerals Corp. conducted a sampling program and detailed geochemical survey to confirm and extend historically identified mineralized zones. Mineralization at the Midway Mine and Picture Rock Quarry was confirmed. The mineralized zones were extended to areas where little previous work has been conducted to the east of the occurrences. Skarn mineralization in the southwest of the Rainbow property gave significant gold and copper values.
